Chapter 159: Detour and Heartbeat

At 7:15 a.m., the rolling shutter of the factory gate was only halfway up. Lin Chen slipped through sideways. As his left foot touched the ground, a dull ache shot through his ankle. Habitually, he shifted his weight to his right leg, taking small, steady steps. The air outside the workshop carried the damp, cold scent of machine oil and rust; breathing it in cleared his head.

The control room door was ajar. Factory Manager Li was already seated at the long table, a half-smoked cigarette pinched between his fingers, the ashtray piled with butts. Lao Wang from the technical department was debugging an oscilloscope, the waveform on the screen jumping erratically. Lin Chen offered no greeting. He set his backpack on the corner of the table and pulled out his laptop. He plugged the power cord into the socket, inserted the USB drive, and waited for the screen to wake. A terminal window popped up. He ran a quick environment check first: Python 2.7, dependency library versions, serial port baud rate. All green lights.

“Power on at nine sharp,” Manager Li said, crushing his cigarette out. His voice was hoarse. “That frequency-reduced polling of yours—don’t stall the machines.”

“Understood.” Lin Chen hit Enter, launching the main process. The log window began to scroll.

At 8:50, the workshop director pressed the master control button. The conveyor belt emitted a low, heavy hum, and the PLC indicator lights flickered on one by one. Lin Chen kept his eyes fixed on the data stream on his screen. It started as scattered garbled text, which was then captured, cleaned, and reorganized by the adaptation layer. The mapping table converting PPI protocol to Modbus TCP kicked in, with latency hovering around 120 milliseconds. Dust motes floated in the morning light, settling into the gaps of his keyboard; he casually covered the touchpad with a tissue.

“Signal strength is at -78 dBm,” Lao Wang said, staring at the wireless bridge monitoring terminal. “It’s about to drop.”

Lin Chen’s fingers hovered over the keyboard. A line popped up in the logs: WARNING: Packet loss > 5%. He didn’t panic. A pre-written threshold check triggered, and the script automatically switched to the branch_fallback.py branch. The polling frequency dropped from twice per second to once every three seconds, and the heartbeat packets shifted to a long-connection keep-alive. The data stream stalled for exactly two seconds before stabilizing. The production counter on the screen kept ticking; it was half a beat slower, but it hadn’t reset to zero.

Manager Li stood up and walked behind Lin Chen. He looked at the neatly arranged JSON data on the screen, then out at the robotic arms operating normally in the workshop.

“Speed drop of 7.3 percent,” Li reported a number. “Half a point better than what your white paper claimed. Acceptable.”

Lin Chen let out a quiet breath, realizing his shirt was already plastered to his back with cold sweat. He saved the logs, generated a CSV report, and pushed it to Manager Li’s intranet email.

“Let the pilot data run for a week first,” Li said, tucking his cigarette pack back into his pocket. “If it stays stable, we’ll sign the formal maintenance contract next month. The fee will be twenty percent off your last quote, but I’ll need you on-site two days a week to track the line. Can you manage that?”

Twenty percent off. On-site. Lin Chen ran the numbers quickly in his head. Even with the discount, the monthly payout would still cover his living expenses for the next two months, plus Xiaoman’s medication. Being on-site meant requesting leave, but Professor Zhou had mentioned earlier that industry-academia projects counted toward practical credits, and the final defense could waive two electives.

“I can,” Lin Chen nodded. “I’ll bring a backup machine. It’ll run even if the network drops.”

Li gave him a look, said nothing more, and turned to leave the control room. Lao Wang patted Lin Chen on the shoulder. “Kid, your code’s solid. We’re taking Professor Zhou out for dinner tonight. You coming?”

“I’ll pass. Still have assignments.” Lin Chen closed his laptop and pulled out the USB drive. When his left foot touched the floor, the ache had already spread down to his calf. He leaned against the wall and made his way out slowly.

By the time he got back to the dorm, it was nearly eleven. His roommate was at the library, and the room was so quiet he could hear the friction of the ceiling fan’s bearings. Lin Chen propped his left foot up on a pillow and applied a hot towel for twenty minutes. Blood circulation gradually returned, and the stiffness in his muscles eased slightly. He sat back down at his desk and opened Lao Zhao’s project folder.

Concurrency stress test script. New standard.

He created a new file: stress_test_v1.py. Lao Zhao’s requirements were clear: simulate five hundred terminals initiating scan requests simultaneously, while monitoring for memory leaks and connection pool overflows. The factory’s network was isolated, but Lao Zhao’s testing environment was in the cloud. That meant he had to use multithreading with queue management, avoid blocking the main thread, and manually control socket timeouts.

His fingers moved across the keyboard. threading, Queue, connection pool configuration. He wrote slowly, running a local unit test for every function he completed. The glow from the screen cast his thin shadow against the wall. Outside, the sky darkened and the streetlights flickered on. He made a bowl of the cheapest instant noodles, drank half the broth, and left the rest to clump in the bowl. He ignored it and kept tuning the parameters.

By nine p.m., the script framework was complete. He imported the mock data and launched the stress test. In the terminal, the concurrency count jumped from 10 to 50, then to 200. The memory usage curve climbed steadily, with no spikes. The connection pool recycled normally. Green lights across the board.

He leaned back in his chair and rubbed his dry, tired eyes. The numbers from his ledger ran through his mind: Lao Zhao’s final payment, the factory’s pilot advance, plus his existing savings—he should finally break into the four digits. He didn’t need to celebrate. He just needed to archive the logs and push the code to his private Git repository.

His phone vibrated. A WeChat message from Lao Zhao.

Reviewed the script. Logic is sound. But before the Wednesday delivery, add a feature: extract the vulnerability signatures from the scan results and categorize them by CVE ID. The ops department wants to import them directly into the ticketing system.

Lin Chen stared at the screen. CVE categorization. That meant integrating an external vulnerability database API and processing massive amounts of unstructured text. The workload would at least double.

He replied: Can do. How will the fee be calculated?

Lao Zhao’s profile picture spun twice before a new line appeared: New standard. Fixed base rate, with a commission per valid entry for feature extraction. Wednesday, 8 p.m. I want the executable.

Lin Chen didn’t reply right away. He opened a draft notebook and wrote down CVE matching algorithm and Regex optimization. The tip of his pen scratched softly against the paper. Outside, the wind died down, and the dormitory building settled into sleep. He closed the notebook and reopened the terminal.

The screen’s glow lit up once more. He typed the first line of code. The road ahead was long, but every step had to be solid.